Multilayered or laminated rubber tubing serving as a fuel transporting hose for an automotive fuel feed line into a vehicle reservoir are available. The conduit wall may have three or more layers; a heat and gasoline-resistant inner tube; a gasoline impermeable barrier layer, an intermediate elastomeric tie layer; a weather-resistant outer tube and a reinforcing fiber matrix or layer interposed and integrated between the outer and intermediate tie layers. Even so, oxygenated fuel adversely affect a fuel hose life so that enhanced gasoline-resistant features are needed.
The US EPA is in the process of establishing new, more restrictive requirements on non-automotive fuel systems that will limit the release of hydrocarbons into the environment.
The State of California, through the California Air Resources Board (CARB), has taken this permeation requirement a step further by requiring a maximum permeation rate of 15 g/m2/day, but the test involves a 1,000 hour pre-test soak step. In addition, the test is performed on circulating fuel, measuring the capture of hydrocarbons permeating through the tube wall and the test temperature is elevated to 40° C. The marketplace does not want to be in a position of having to use one tube/hose for California and another for the rest of the US, so it is critical that a small engine, non-automotive fuel line meets the most rigorous requirement of CARB.
It is difficult to pass the CARB requirement with tube/hose made of thermoplastic materials. Most tubes/hoses that would meet such stringent requirements are made of thermoset materials. Thermoset tubes do not lend themselves easily to flexibility, sizing, continuous length, customization and are opaque.
Therefore, a need remains for tubing that would meet the CARB requirements and fulfills one or more of the current disadvantages of current products.